Level 3: Science Diploma Unit 16: Assignment A
The Sun and its Family
Emma Padgett
A solar system is where objects in space orbit around one host star. Our solar
system consists of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus and Neptune; dwarf planets: such as Pluto and dozens of moons and
millions of asteroids, meteors and comets.
The inner planets are the first four planets in the solar system, closest to the
sun: Mercury, Venus, Earth and Mars. They are also known as The Terrestrial
Planets. These dense and small planets are made from rock and iron with few
moons, kept in orbit by the gravitational pull of the sun. The closest planet to
the sun is Mercury.
Formed around 4.5 billion years ago, Mercury is the smallest planet, with its
2439.7km radius, and the closest to the Sun, being at a distance of about 36
million miles from the sun, however, is the second hottest surface, with
temperatures of 430 degrees Celsius during the day, which drop to -180
degrees Celsius at night because the planet doesn’t have the
atmosphere to retain the heat.
It is only slightly larger than the moon of the earth. With the
rocky and cratered surface, it is very unlikely any life could
survive on this planet. Its orbit is not perfectly spherical, it is
more like an egg shape, so it takes Mercury from 2.9 AU from
the sun to 4.3 AU from the Sun. It spins very slowly on its axis and completes
one rotation every 59 Earth days. When the planet is at the closest to the Sun,
it doesn’t have a sunrise or sunset like most other planets; the morning sun is
believed to rise briefly, set and rise again on some parts of the surface. This
then happens in reverse at sunset for other parts. Therefore, one full day to
night cycle is 176 days on Earth. The axis the planet is at is only 2 degrees,
which means it is upright and doesn’t experience seasons like many other
planets.
Mercury has an exosphere (instead of an atmosphere), composed of:
• oxygen,
• sodium,
• helium,
• hydrogen
• potassium
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It was created by atoms blasted off the surface by solar wind and
micrometeoroid impacts. It is the second densest planet, after earth. Around
85% of the planet’s radius, about 2074km, is a metallic core, which has shown
evidence of being partly liquid. In contrast, the outer shell to Mercury is 400km
of cratered rock and if we were to stand on the surface, it would be a lot
brighter than the Earth and the sun would appear three times as large as it
does on our surface. Meteors that collided with the planet has left the
grey/brown surface scarred with large craters. These features have even been
named after famous artists in the past industries, such as Dr Seuss. The largest
basins, including Caloris, which is 1550km in diameter, would have been
created by asteroid impacts from the early solar system history. However,
there are also large areas of smooth terrain and even cliffs, which can be
hundreds of miles long and up to a mile high, because of the cooling of the
interior of the planet. Another feature of the surface would be the bright
streaks: The Crater Rays. These are from large comets striking the surface with
a tremendous amount of energy. This extreme amount
of energy is so powerful it creates a hole in the ground,
crushing rock under the point
of impact. The crushed rock is thrown far from the
planet and then falls to the surface, creating the rays.
The “light” is created by the small pieces of crushed
rock reflecting the sun better than the large bits of
rock, due to small surface area.
Again, forming 4.5 billion years ago, Venus is the second closest planet to the
sun, being 108,115,295km from the sun. It spins very slowly, in the opposite
direction the other planets. It is a very similar size to Earth, as it is 6052km is
radius, however, has very different conditions. The planet surface is the
hottest in the solar system, this is due to the thick atmosphere being 97%
carbon dioxide, which causes the greenhouse gas effect, so the surface reaches
500 degrees Celsius, which is hot enough to melt lead. However, the
atmosphere is in layers and many of them at different temperatures; the layer
in which the clouds are is around the same temperature of the Earth’s surface.
The planet is one of the only planets to rotate east to west, with only Uranus
doing this too. It completes of rotation in 243 Earth days, which is the longest
day of any planet in the solar system. On Venus, one day-night cycle is 117
Earth days as it rotated in the direction opposite its orbital revolution in the
sun. The orbit is nearly a perfect circle, it has the most circular orbital of them
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all, most planets have oval shaped orbitals. Venus also has an axis tilt of 3
degrees so spins upright and therefore doesn’t experience seasons.
Nevertheless, the top level of clouds, that go around the planet every 4 Earth
days, travel at 224 miles per hour, with atmospheric lightning bursts lighting
them up. The lower down the clouds are, the slower they move. Scientists
believe the clouds at the surface only move a few miles an hour.
The structure of the planet is much like Earth’s: iron core, approximately
3200km in radius; mantle, made of hot rock; and a surface that is a thin crust
of rock that moves as Venus’ mantle shifts to create volcanoes. From space,
Venus appears white as it is covered in a layer of
clouds, made from sulphuric acid, that reflect and
scatter sunlight. At the surface the rocks vary in shades
of grey, which look orange of the surface because of
the atmosphere filtering the sunlight. It has many
surface features such as mountains, valleys, and
thousands of volcanoes. The highest mountain is called
Maxwell Montes and is 20000 feet high, again similar to Mount Everest.
Because of the temperatures and lack of water, the landscape is very dusty.
There are two highland areas on Venus: Ishtar Terra, in the North, which is the
size of Australia. And Aphrodite Terra, in the south, which is straddling the
equator for 10000km. The planet is covered in craters, none smaller than 0.9
miles in diameter, made from small meteoroids burning up in the dense
atmosphere. All these surface features are named after important women,
both fiction and non, such as “Diana, Goddess of the hunt” is the name of a
deep canyon.
Humans couldn’t survive on Venus due to high temperatures and extreme
pressure. The spacecraft sent to Venus doesn’t last very long as the
temperatures overheat electronics so scientists can’t explore the surface up
close.
The third planet is Earth. Scientists call Earth’s orbit position “The Goldilocks”
as it is the “Just right” conditions for life to survive. It is the only known planet
to support life, with its 20 degrees surface, life can continue to reproduce and
survive in these conditions. Scientists believe when planets were first formed
by the gravitational pull upon rock, no water was on the planet and only
arrived when comets filled with liquid bombarded the earth and left the water
, 4
we have today. Earth is the biggest terrestrial planet and the fifth biggest
overall, with a radius of 6371km. It is exactly 1AU from the Sun, so the light
takes around eight minutes to reach our planet. Earth takes 365.25 days to
complete one trip round the Sun. The scientists add an extra day every four
years to keep our calendars consistent; this is called a
leap year. Our planet has an axis of rotation of 23.4
degrees. This tilt causes Earth to experience seasons:
when the northern hemisphere is tilted towards the
sun during rotation, the Sun will be higher in the sky
and produce summer. On the other side, when the
southern hemisphere is towards the
Sun, there will be less solar heat, so winter is
produced. Six months later the roles are reversed.
Earth has four layers: inner core, outer core, mantle and crust.
• The inner core:
o Solid sphere made from iron and nickel metals
o About 1221 kilometres radius
o Temperature is 5400 degrees
• The outer core:
o 2300 kilometres in radius
o Made from iron and nickel fluids.
• The mantle:
o The thickest layer
o Hot mixture of molten rock
o 2900 kilometres thick
o “Caramel” consistency
• The crust:
o 30 kilometres thick
o At the bottom of the ocean, it is only 5 kilometres thick
Scientists believe the planet formed 4.5 billion years ago approximately. It
would’ve formed by gravity pulling a swirling gas and dust to become a planet.
The surface is very similar to its neighbours with volcanoes, mountains and
valleys. The ocean covers 70% of the planet’s
surface and contains 97% of all Earth’s water.
Almost all of the volcanos on the planet are
hidden by
the ocean such as Hawaii’s Mauna Kea, which is
taller than Mount Everest but most of it is
underwater. Earth’s longest mountain range is
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